| 摘要 |
PURPOSE:To prevent the generation of an error of a demodulated signal, by comparing the zero-cross space obtained by counting clocks with the reference value which is switched in response to the demodulated signal to obtain the demodulated signal. CONSTITUTION:An input FSK signal is supplied to a limiter amplifier 12 via a BPF11, and the zero-cross position is made clear. Then the FSK signal is turned into a signal of a prescribed voltage level through a comparator 13 and fed to an input/output port 15 of a microprocessor 14. The processor 14 measures the zero-cross spaces ZCN...ZCN-6... of the input signal by counting clocks. Then an accumulator ACC and an arithmetic circuit ALU which are stored in storage regions RZC0...RZC6... of an RAM compare the measured zero-cross spaces with the reference value. The result of this comparison is turned into a demodulated signal RD. In this case, the reference value is set at a high level when the signal RD is 0 and at a low level when the signal RD is 1 respectively. |
